This invention relates to a flow tube having a low pass filter positioned in the flow path. Specifically a noise attenuation plate cooperates with ribs formed on internal surfaces of the flow tube to reduce high frequency whistle generated by a turbo charger.
The use of a turbo charger is a simple, compact, and effective way to increase engine power without increasing the size of the engine itself. Turbo chargers allow an engine to burn more fuel and air by packing more into existing engine cylinders. Typically, turbo chargers are attached to an engine exhaust manifold with exhaust from the cylinders causing a turbine to spin. The turbine is connected by a shaft to a compressor, positioned between an air filter and an intake manifold, which pressurizes air going into the cylinders. Both the turbine and the compressor include blades or impellers, which turn at very high speeds during operation.
As the blades rotate, a high frequency whistling noise is generated, which is undesirable. Traditionally, an absorptive material is used to dissipate the unwanted acoustic energy. However, the use of this material increases the risk of engine contamination and can lead to increased engine maintenance or premature engine failure. Further, installation of the absorptive material increases assembly time and cost.
Thus, it is desirable to have a method and system for reducing noise generated by a turbo charger without risking engine contamination, as well as overcoming the other above mentioned deficiencies with the prior art.
A flow tube for an induction system includes an inner surface that defines a flow path. A plate is positioned in the flow path to form a low pass filter. The low pass filter attenuates high frequencies while permitting low frequencies to flow through.
In a preferred embodiment, the flow tube includes a plurality of rib members formed on the inner surface. The ribs are longitudinally spaced apart from one another along the length of the flow tube. Preferably, each ribbed is spaced at a predetermined equal distance from the next rib. The ribs and plate positioned within the flow path, cooperate to attenuate frequencies above a predetermined level as acoustic energy generated by a turbo charger enters the flow path.
Preferably, the plate includes a plurality of tuned holes that are used to attenuate high frequencies. The holes can be of varying diameter and varying depth. Further, the holes can be formed in a symmetric or non-symmetric pattern on the upper and/or lower surfaces of the plate.
The flow tube is preferably used in an induction system for an engine with a turbo charger. When the high frequency acoustic energy generated by the turbo charger encounters the rib and plate formations, the change in impedance causes reflections back toward the turbo charger. Thus, the plates and ribs form a low pass filter mechanism that significantly reduces the high pitch whine generated by the turbo charger.
The subject system and method reduces the magnitude of undesirable noise while eliminating the risk of engine contamination. These and other features of the present invention can be best understood from the following specifications and drawings, the following of which is a brief description.